…ainer config

- Added DEVCONTAINER arg/env in Dockerfile to enable conditional zsh install
- Updated devcontainer.json to set build target to "dev" and pass DEVCONTAINER=1
- Removed "remoteUser": "appuser" to prevent container crash
- Replaced old GitHub CLI feature key with updated version
- Added VS Code extension recommendations for Python, Prisma, Ruff, etc.
- Removed deprecated pre-commit feature

trailing comma in devcontainer.json...